The present invention is related to the field of wood flake production.
More specifically, the invention is related to a wood flake having a first, concave surface and a second, convex surface delimiting between them the essentially wedge-shaped flake, the surfaces converging in an imaginary tip outside the flake, the tip being located on a centerline extending between the surfaces, and outside the flake by a centerline section.
Still more specifically, the invention is, further, related to a method of producing an essentially wedge-shaped wood flake, in which the flake is chipped from the wood by means of a rotating chipping tool, such that it comprises a first, concave surface and a second, convex surface delimiting between them the flake.
The invention, moreover, is related to a method of profiling a log, in which longitudinally extending corners are chipped from the log and side planks are sawn from the log, the side planks having a narrow surface configurated by one of the side surfaces of the corner, a saw cut being executed along the other side surface prior to chipping out the corner.
Moreover, the invention is related to an apparatus for producing an essentially wedge-shaped flake in which the flake is chipped from the wood by means of a rotating chipping tool, such that it comprises a first, concave surface and a second, convex surface delimiting between them the flake.
Further, the invention is related to an apparatus for profiling a log, comprising a chipping tool for chipping longitudinally extending corners from the log, means for sawing side planks from the log, the side planks having a narrow surface configurated by one of the side surfaces of the corner, a saw being provided for executing a saw cut along the other side surface prior to the chipping of a corner.
Finally, the invention is related to uses of the afore-mentioned wood flake, the afore-mentioned method as well as the afore-mentioned apparatus.
In the technology of wood processing it is generally known to partially or entirely chip wood by means of so-called chipping tools. Chipping tools are conventionally rotating tools having chipping knives along their periphery. Chipping tools are conventionally mounted stationarily and the wood to be partially or entirely chipped is guided along the chipping head in an axial direction of the wood.
Due to these circumstances, the wood flakes so generated have a wing-type shape with an essentially wedge-shaped cross-section. The wood flakes are delimited on their two large surfaces by a concave and a convex side, respectively, wherein these sides extend from a thick end of the wood flake towards a narrow end or, speaking in terms of a cross-sectional view, towards a tip in which the two surfaces converge tangentially.
Wood flakes are a valuable raw material for various industrial areas. Among these are the cellulose industry, the paper industry but also manufacturers of wood materials and so-called composite components, i.e. planks, boards and beams produced by gluing together wood flakes.
These wood flake processing industries accept wood flakes according to a specific classification. Wood flakes of medium size are highly preferred because when the wood flakes are too large, they are difficult to process and, if the wood flakes are too small or too thin, then during the production of cellulose, paper, wood materials or composite components losses occur or insufficiently stable structures are obtained.
The classification of wood flakes supplied is the decisive criterion for the price which the wood processing industry is prepared to pay for such wood flakes. Therefore, within the wood processing industry there is an important demand that, during the production of wood flakes as much as possible such wood flakes shall be produced which within the classification of the wood flake processing industry given will achieve the highest price.
If wood flakes are produced by means of a rotating chipping tool, as described above in more detail, they have a thinly terminating end along their wedge-shaped cross-section. This thin end is a disadvantage for the further processing of such wood flakes because the thin end will either entirely be dissoluted within the pulp or will result in less stable areas during the production of composite components.
In practice, wood flakes are produced by either entirely chipping wood into wood flakes or by chipping wood flakes out of the wood.
A partial chipping of wood, for example, takes place in the course of the so-called profiling of logs. This term is to be understood to mean an all-side processing of the initially raw log for giving it a predetermined cross-sectional shape (profile) so that the profiled log during subsequent sawing may easily be dissected into boards and beams. A corresponding method together with an appropriate apparatus is, for example, disclosed in DE 29 28 949 A.
According to these prior art methods and apparatuses, the logs are worked by means of so-called corner millers prior to the profiling which, in an axial direction mill corners from the log so that the log, having been flattened before or being flattened thereafter, assumes a profile from which so-called side planks may be sawn away.
DE 37 02 980 C2 discloses a corresponding method together with an appropriate apparatus. According to the prior art method a first, for example horizontal saw cut of a predetermined depth is applied first from one side of the log, wherein in that case the axis of rotation of the saw blade extends vertically. After the application of the saw cut or (when a combined tool head is utilized) simultaneously thereto a partial area of the wood above the saw cut is chipped away, wherein the rotational axis of a chipping tool or, respectively, in a combined tool head the common rotational axis, extends vertically. The area chipped away does not extend as far in a horizontal direction into the log as the first saw cut is deep. Thereafter, in a further working step the residual area above the horizontal saw cut is chipped away, namely by means of a chipping tool, the rotational axis of which extends horizontally in the given example. Thereafter or together with the chipping away process step a second, vertical saw cut is applied in which the bottom of the groove so generated lies with its center where the first, horizontal saw cut was terminated within the wood. As a result, an area is worked out of the log being similar to a corner, however, being stepped at the bottom of the corner. It is important to note at this instance that never one of the two chipping tools engages an area that had been sawn before. In this prior art method, so-called xe2x80x9ccomma chipsxe2x80x9d are exclusively generated likewise as was described above.
EP 0 770 461 A2 discloses a method and an apparatus for dissecting logs into small wood products. According to this method the log is profiled in that first the corners are entirely sawn away by means of circular saw blades having axes being oriented 90xc2x0 with respect to each other. During the sawing out wood strips are generated that have to be removed from the profiling installation and have to be chipped in a separate chipping machine.
EP 0 775 558 A1 discloses a method for working logs. According to this method a band saw is first guided longitudinally through the log, the saw cut being positioned such that it separates a side plank from the log. A separator element follows the saw blade along the sawn gap so as to keep the side plank being still integrally connected to the log in a distance from the remaining wood piece. A combined edging tool follows the separator element which, as already described above, consists of a chipper and a circular saw blade connected therewith. By means of this tool, the corner area above the narrow side of the side plank to be produced is chipped away and, concurrently, the narrow side of the side plank is worked by the circular saw blade in a high surface quality. Within the chipping tool the chipping knives and the circular saw blade have the same cutting radius. The cutting circle extends tangentially relative to the broad side of the side plank to be separated, in other words, the saw teeth and the chipping knives do not run into the groove generated by the band saw acting upstream. However, also if in this prior art method the cutting circle of the chipping knives were to extend into the groove, this would have no consequences within the scope of the present invention because band saws, as well known in the art, only generate extremely narrow kerfs which, typically, have a maximum width of 3 mm. Therefore, only the outermost tips of the flakes would be affected. This, however, would only result in an unimportant modification of the flake shape. Therefore, according to this prior art method, only the already mentioned xe2x80x9ccomma chipsxe2x80x9d are generated by principle.
According to all afore-mentioned prior art methods and apparatuses, therefore, conventional wood flakes having a thinly converging end on the one hand and saw dust on the other hand, are generated.
DE 43 37 682 C1 discloses a method and an apparatus for dissecting a log.
According to the prior art method, side planks are sawn away from a laterally flattened log by means of a circular saw, the side planks being still provided at their edges with barks. These side planks, as long as they are still integrally connected with the log at their upstream end, are bent away and, thereafter, run essentially parallel to the log at a distance thereto. Within this distant position the side planks are chipped at their narrow sides by means of an edging chipper and are, hence, edged. The cutting edges of the edging chipper extend under approximately 45xc2x0 angle of engagement in a radial direction through the wood when in the vicinity of the barks. The side planks, therefore, almost run in the area of the rotational axis of the edging chippers and past the latter. This is possible because, as mentioned above, the side planks at this moment are guided at a lateral distance from the main wood. The purpose of this measure is to generate so-called xe2x80x9cuniform thickness chipsxe2x80x9d during the edging of the side planks having been bent away before, i.e. chips which, in contrast to the so-called xe2x80x9ccomma chipsxe2x80x9d have an essentially constant thickness parallel to the wood fiber. These xe2x80x9cuniform-thickness-chipsxe2x80x9d have approximately the cross-sectional shape of a parallepiped, the corner angle of which being about 45xc2x0 (and 135xc2x0, respectively) because the plane of engagement of the chipper on the wood lies, as mentioned above, under approximately 45xc2x0 relative to the direction of movement of the side plank.
This prior art method and the corresponding apparatus, therefore, have the advantage to generate chips being advantageously configured for a subsequent processing within the cellulose industry, however, this disadvantage may only be obtained with substantial additional efforts because the side planks have to be bent away from the sawing plane and have to be edged in a significant distance from the main wood. However, this is not possible in the same manner for all woods, at least not without damaging the fiber of the side plank during the bending away.
It is, therefore, an object underlying the invention to improve a wood flake as well as methods and apparatuses of the type specified at the outset and the above-mentioned uses, respectively, such that the afore-mentioned disadvantages are avoided. In particular, it shall become possible to produce wood flakes in an economically optimum manner and with a shape corresponding exactly to those classes of wood flakes for which the wood flake processing industry is ready to pay the highest prices.
In a wood flake of the type specified at the outset, this object is achieved according to the invention in that the length of the centerline section lying outside the flake has between 40% and 100% of the length of the centerline section inside the flake.
In a method of producing a wood flake of the type specified at the outset, this object is achieved according to the invention in that prior to the chipping the wood is removed in the area in which the surfaces converge in an imaginary tip.
In a method of profiling a log of the type specified at the outset, this object is achieved according to the invention in that the chipping tool has a cutting radius extending into the groove generated by the saw cut and running free therein.
In an apparatus for producing a wood flake of the type specified at the outset, this object is achieved according to the invention in that means are provided for removing the wood in the area in which the surface is converged in an imaginary tip prior to the chipping.
In an apparatus for profiling a log of the type specified at the outset, this object is achieved according to the invention in that the chipping tool has a cutting radius extending into the groove generated by the saw cut such that it runs fee therein.
Moreover, this is object is achieved by the use of the afore-mentioned wood flakes as strands during the production of composite beams or planks.
Further solutions according to the invention consist in the use of the afore-mentioned method as well as the afore-mentioned apparatus for chipping out edges during the profiling of logs.
The object underlying the invention is thus entirely solved.
In contrast to conventional, wedge-shaped chips having a thinly extending terminal end or tip, respectively, the invention suggests to remove that thinly terminating end so that only the thicker end of the wood flake survives.
A shortened wood flake of that kind has much more economical value and, hence, may be processed much more advantageously. The operator of a saw mill may, hence, expect a significantly higher economical yield during the processing of wood flakes if wood flakes of that shape are used.
The fact that the tip lies on a centerline of the chip extending between the surfaces, and outside the wood flake by a centerline section, the length of which being between 40% and 100% of the length of the centerline section within the wood flake has the advantage that a wood flake is provided being exactly shortened to an extent being an economical optimum.
Moreover, it is preferred when the centerline at the junction between the centerline sections intersects the flake in a boundary surface. The boundary surface, preferably, and the centerline enclose between them a thinned angle so that, still more preferably, the wood flake has a thickness of between 2 and 10 mm between the surfaces at the transition between the convex surface and the boundary surface.
These dimensions, too, have the advantage that a wood flake is generated that may be exploited under optimum economical conditions.
The considerations made above in connection with the embodiments discussed before, likewise apply for corresponding embodiments of the inventive method as well as for the inventive apparatus.
Moreover, it is particularly preferred when the boundary surface is plane. Preferably, this is effected by making the boundary surface through sawing.
The saw, preferably, is configured as a circular saw having a circular saw blade of more than 5 to 6 mm thickness. The circular saw is, still more preferably, followed by a wood cleaver extending between the saw and the chipping tool.
This measure opens up the possibility to prepare during one and the same operational step the wood to be entirely or partially chipped by a cut, in particular by a saw cut, such that for a subsequent engagement of the rotating chipping tool the afore-mentioned shortened wood flakes are generated, almost immediately because that area had been removed before in which the thinly converging ends or tips, respectively, would have been made.
Further advantages will become apparent from the drawing and the enclosed description.
It goes without saying that the features mentioned before and those that will be explained hereinafter may not only be used in the particularly given combination, but also in other combinations or alone without leaving the scope of the present invention.